The invention offers a process of more effective use of the deformation zone of a motor vehicle body of graded rigidity and a device enabling the application of the process.
There exist motor vehicle bodies of graded rigidity in which the passanger compartment represents the relatively most rigid part of the body while the less rigid front and rear parts of the body represent a deformation zone serving for the absorption of the energy generated by possible collision of the vehicle with a foreign body or vice versa. However, due to the considerations of design, certain rigid and difficult to deform vehicle parts are also situated in such deformation zones. These are, for example, the vehicle driving gear, road wheels and, in some cases, the spare wheel. In case of deformation of the deformation zone, these parts remain basically undeformed as they "bridge" a certain part of the deformation zone and tend to transfer a part of the unabsorbed impact energy to the passenger compartment, thereby threatening the lives or health of the motor vehicle passengers.
The effectively used length of the deformation zone can be expressed on the basis of the following formula: EQU L.sub.S L.sub.C -L.sub.t
where
L.sub.S =effectively used length of the deformation zone, PA0 L.sub.C =total length of the deformation zone, PA0 L.sub.t =length of the largest rigid body situated in the deformation zone or, sum of the lengths of the rigid bodies situated one after the other in the deformation zone.
There exist motor vehicles designs using front engines. In case of head-on collision, the front deformation zone deforms, while the engine and the gearbox are forced under the passenger compartment. In this case, the vehicle driving unit does not "bridge" any part of the deformation zone, allowing thus for better absorption of the impact energy. Other voluminous and relatively rigid bodies which are situated in deformation zones of motor vehicles and, in case of collision, reduce the length of the deformation zone, are motor vehicle wheels, both road wheels and the spare wheel. Two solutions are being used to prevent deformation of the passanger compartment by a road wheel or spare wheel--either through increased rigidity of the passanger compartment in the areas of anticipated pressure by a wheel or, through the extension of the deformation zone in front of the vehicle wheels (in the direction of the impact). The former measure results into increased weight of the body and quantity of work in its manufacture while the latter, in addition, increases the total length of the vehicle body.